What Imeo is suggesting doing is what is called in the thread industry as an "interference thread". It cannot, I repeat, cannot be used in this application, interference threads are only allowable in applications that are not dis-assembled on a regular basis. They can only be used a few times before they lose their friction. Within a week the threads will self clearance themselves and have no more holding power then any thread.
Another serious problem is the direct contact with batteries as they take virutually no pressure to deform. I repeat that there is a reason that the millions of products produced over the past 100 years do not use a direct clamping action on both ends of the battery to maintain electrical contact. You need some sort of spring, even if it is simple as a u shaped piece of copper on one end that absorbs the load, exerts constant pressure and protects the soft battery ends.
Both of these are serious design flaws in this product and will produce an extremely unreliable product and electrical connection. No amount of wishful thinking or reassurance by the designer will negate these problems. I understand that he is new to designing, but these are fundamental issues that the designer needs to come to terms with.
I think what you suggested, Iken, could be viable. Some sort of rachet system that would not allow the screw in section to back off, thus losing electrical contact, however, it would need to be used in conjuction with a spring. A rachet system, however, would require, relatively speaking, very complex machining and engineering.
I personally love 801 especially at 6 volts.
